The Edmonton Oilers and their scouts have spent countless hours researching different players in different leagues. Leagues like the USDP and the WHL are well represented in the first round of this draft. Last year it was the SWE and the OHL. in 2017 it was the WHL and the OHL and in 2016 it was Finland and the OHL. You can keep going back and see that there is a correlation between the leagues of the top two players and those with the most ranked in the first round.
You can argue that since the scouts are often watching players from a certain league, that they feel more comfortable recommending them.